Conventional articles of footwear generally include two primary elements, an upper and a sole structure. The upper is secured to the sole structure and forms a void on the interior of the footwear for securely and comfortably receiving a foot. The upper is generally formed from multiple elements that are stitched and adhesively bonded together to form a comfortable structure for receiving the foot. More particularly, conventional footwear may include, for example, an exterior formed of leather and textile materials that are resistant to abrasion and provide the footwear with a particular aesthetic. Foam materials may be located on the interior of the upper to enhance the comfort of the upper, and moisture-wicking textiles may be positioned adjacent the foot to limit the quantity of perspiration within the upper.
The sole structure attenuates ground reaction forces and absorbs energy as the footwear contacts the ground, and often incorporates at least two discrete layers that are conventionally referred to as a midsole and an outsole. The midsole forms the middle layer of the sole and serves a variety of purposes that include controlling foot motions, such as pronation, and shielding the foot from substantial ground reaction forces. The outsole forms the ground-contacting element of footwear and is usually fashioned from a durable, wear resistant material that includes texturing to improve traction. The sole structure may also include an insole, which is a thin, impact attenuating member located within the upper and adjacent to a sole of the foot to enhance footwear comfort.
Flexibility in the article of footwear aids in performance, durability, comfort, etc. of the article of footwear. Accordingly, an article of footwear having increased or improved flexibility throughout the article of footwear is desired.